This invention relates to a floating disk brake used for braking of a vehicle, more specifically a floating disk brake which can reduce uneven wear of friction pads (hereinafter simply referred to as pads) and thus reduce fading.
FIG. 4 shows a typical floating disk brake. It comprises a rotor 5 (disk rotor), a pair of pads 4-1 and 4-2 provided on both sides of the rotor 5 to face the braking surfaces of the rotor, and a caliper 1 formed with a cylinder in which is slidably received a piston 3 so as to oppose one of the pads, i.e. the pad 4-1. The caliper 1 further includes an outer claw 1a provided so as to face the other pad 4-2. The pad 4-1 is pressed by the piston 3 against the rotor 5, while the other pad 4-2 is pressed against the rotor 5 by the outer claw 1a, which is moved toward the rotor by reaction force when the piston 3 is moved toward the rotor. Both pads are thus brought into frictional contact with the rotor, thus applying braking force to the rotor.
This floating disk brake further includes slide guide portions 6 through which the caliper 1 is supported on a mount (stationary member) 2 so as to be slidable in the axial direction of the rotor 5. Each slide guide portion 6 comprises a slide pin 6a extending in the axial direction of the rotor and fixed to one of the caliper 1 and the mount 2 (caliper 1 in the example of FIG. 4), and a pin hole 6b formed in the other of the caliper 1 and the mount 2 (mount in the example of FIG. 4) to slidably receive the slide pin 6a. In order that the caliper 1 can move freely following any run-out or thermal deformation of the rotor 5, a fairly large clearance is provided between the slide pin 6a and the pin hole 6b of each slide guide portion 6. Further, in order to suppress rattling sounds of the caliper, a rubber bushing (not shown) is disposed between the slide pin 6a and the pin hole 6b of each slide guide portion 6.
A floating disk brake of this type is shown e.g. in Japanese utility model publication 7-19629.
By providing a large clearance between the slide pin and the pin hole of each slide guide portion to improve the followability of the caliper to any run-out or thermal deformation of the rotor, the caliper can move fairly freely in the radial and tangential directions of the rotor.
If the caliper 1 can move relatively freely in the tangential direction of the rotor, it tends to swing as shown by chain line in FIG. 4 during braking. This creates variation in the surface pressure distribution of the pads, which in turn increases uneven wear of the pads 4-1 and 4-2 in the tangential direction of the rotor. Uneven wear will shorten the life of the pads and promote fading.
One way to prevent this problem is to reduce the tangential (with respect to the rotor) clearance between the slide pin 6a and the pin hole 6b of each slide guide portion 6 compared to the radial (with respect to the rotor) clearance between the slide pin and the pin hole of each slide guide portion by e.g. forming the pin holes 6b in an oval shape (in cross-section), or forming a chamfer on each slide pin 6a so as to reduce only its diameter extending in the radial direction of the rotor. But it requires large expenses to form such complicated pin holes or slide pins.
An object of the present invention is to provide a floating disk brake having a caliper designed so as to be movable more freely in the radial direction of the rotor following any run-out or thermal expansion of the rotor and movable less freely in the tangential direction of the rotor to suppress uneven wear of the pads, thereby prolonging the life of the pads and reducing the possibility of fading at a minimum cost.